The present invention relates to a device for stretching limbs and joints. More specifically, to a stretching device that allows precise stretching throughout the joint range of motion including the extreme positions where spasticity and contracture are most significant.
Neurological impairments including stroke, spinal cord injury, multiple sclerosis, and cerebral palsy are the leading causes of adult disability, resulting in spasticity and contracture as one of the largest lasting effects in patients. The hypertonus and reflex hyperexcitability disrupt the remaining functional use of muscles, impede motion, and may cause severe pain. Prolonged spasticity may be accompanied by structural changes of muscle fibers and connective tissue, which may result in a reduction in joint range of motion. For example, stroke patients may develop considerable ankle spasticity or contracture and walk with xe2x80x9cdrop-foot.xe2x80x9d An ankle-foot orthosis is often used to stabilize the ankle and correct the foot-drop. Though the ankle-foot orthosis helps support the ankle and provides toe clearance during the swing phase of a gait stride, it may force adaptive behavior on the patients by interfering with ankle plantarflexion and alter the need for muscles to contract at the appropriate time and intensity throughout the gait cycle. The latter may have significant adverse effects on the recovery of the patient""s motor control capability. Lack of mobilization may also risk development of contracture, changes in connective tissue length and the number of sarcomeres in muscle fibers.
Physical therapy has long been in use as a mode of rehabilitation for treating persons with spastic limbs or contractured joints. Most often people are afflicted with these types of disabilities from strokes, as discussed herein, spinal cord injury, cerebral palsy, or multiple sclerosis, although affliction can be caused through other diseases and traumatic injuries as well.
Typically, a physical therapist uses physical modalities and physical manipulation of a patient""s body with the intent of reducing spasticity and contracture, thereby restoring limb and joint function. Unfortunately, the effects may not be long-lasting, partly due to the limited and sometimes infrequent therapy a patient may receive. Furthermore, the manual stretching is laborious and the outcome is dependent on the experience and subjective xe2x80x9cend feelingxe2x80x9d of the therapists. Patients may try to restore function to the limbs and joints themselves. Unfortunately, most of the time it is difficult for the patient to have controlled movement without the assistance of a therapist. In addition, it may be difficult for a patient with an impaired limb or joint to maintain continuous motion and resistance to the limb for the treatment to be effective. Of large concern for patients who attempt to rehabilitate on their own is the potential for an increase in injuries due to lack of knowledge or from overexcessive rehabilitation.
For both patients and therapists, there is a need for a device that can stretch and mobilize the joint accurately, reliably and effectively. Furthermore, there is a need for a device to reduce spasticity and contracture that is portable and one that patients can conveniently use in the comfort of their own home such that treatment will be more frequent and provide longer-lasting improvement for the patients.
A number of devices have been developed to exercise the joint and reduce joint spasticity and contracture. One example of the prior art, and one that is generally representative of such prior art devices, discloses serial casting which fixes the limb at a corrected position. This method has been used to correct and treat ankle plantar-dorsi-flexion contracture. Dynamic splinting and traction apply a continuous stretch to the joint involved through an adjustable spring mechanism. This continuous passive motion (CPM) device is widely used in clinics and in a patient""s home to move the joint within a pre-specified range, to prevent postoperative adhesion and to reduce joint stiffness. However, existing devices like the CPM machine move the limb or joint at a constant speed between two preset joint positions. Because the machine must be set between two preset positions, normally between the flexible part of the joint range of motion, the passive movement does not usually stretch the extreme positions where contracture and spasiticity are most significant. If a CPM machine is set too high, at a higher rate of speed or to stretch where the contracture and spasiticty are most significant, there is an increased potential of risking injury to the joints because the machine operates at a constant velocity without incorporating the resisting torque generated by the soft tissues. Obviously, significant damage can be done to the joint or limb if the CPM is set too aggressively. Therefore, a need exists for a device that can safely stretch the joint to its extreme positions with quantitative control of the resistance torque and stretching velocity. In addition, there is a strong need for quantitative and objective measurements of the impairment and rehabilitation outcome.
What is needed is a limb and joint therapeutic device to stretch a spastic or contractual joint repeatedly to the extreme positions until a pre-specified peak resistance torque is reached with the stretching velocity controlled precisely based on the resistance torque.
What is further needed is a limb and joint therapeutic device that will evaluate changes in the mechanical properties of spastic joints including changes in passive joint range of motion, joint stiffness and viscosity, and energy loss.
The present invention satisfies the need for a device that can safely stretch the joint to its extreme positions with quantitative control of the resistance torque and stretching velocity. The present invention provides for a limb and joint therapeutic device that changes velocity in relation to the resistance torque throughout the joint range of motion corresponding directly to a patient""s spasticity or contracture.
The present invention further satisfies the need for a limb and joint therapeutic device that is small and portable. Furthermore, the device satisfies the need for a stretching device that can stretch and mobilize the limb or joint accurately, reliably and effectively. Finally, the device satisfies the strong need for quantitative and objective measurements of the impairment of the patients"" spasticity or contracture while providing a means for reliably detailing the rehabilitation outcome.
According to the embodiments of the present invention, there is a limb and joint therapeutic device for use by both therapists and patients, whether at home or at a clinic. The limb and joint therapeutic device has a limb support, the limb support securing a limb such that the limb is rotatable with respect to a joint. The device has a motor and a motor shaft, the motor and shaft rotating the joint at a variable velocity. A controller communicates with a torque sensor and the motor such that as the resistance torque from the limb increases, the controller communicates to the motor to decrease the variable velocity.
The above advantages, features and aspects of the present invention are readily apparent from the following detailed description, appended claims and accompanying drawings.